Electroporation has become the preferred method for gene transfer due to its ease and efficiency of operation in comparison to alternate techniques. To date, electroporation has been utilized to transform a wide variety of cell types including mammalian cells, plant protoplasts, bacteria, fungi and yeast. The technique involves subjecting cells to a high voltage electric field, which results in the temporary formation of pores in the membrane, thereby allowing exogenous DNA to enter the cells. For example, laboratory strains of the yeast Saccharomyces cerevisiae have been transformed through electroporation with either self-replicating plasmids or by integration of linearized plasmid DNA in the host genome.
Yeast provide an attractive alternative to prokaryotes as host organisms. They can be used for large scale fermentations and are adaptable to continuous fermentation processing. In addition, they are not susceptible to phage infection and generally require only semi-sterile conditions. Conveniently, these cells may be immobilized for the production of metabolites and enzymes.
A number of yeast strains have been used as host organisms for recombinant gene expression.
References describing transformation of S. cerevisiae by electroporation include Hashimoto et al., Appl Microbiol Biotechnol (1985) 21:336-339; Karube et al., FEBS (1985) 182:90-94; Rech et al., Nucleic Acids Research (1989) 18:1313; Simon and McEntee, Biochemical and Biophysical Research Commmunications (1989) 164:1157-1164; Dolorme, E., Appl. Environ. Microbiol (1989) 55: 2242-2246; and Becker and Guarente, Methods in Enzymology (1991) 194: 182-187. Transformation of S. cerevisiae with alkali cations or thiol compounds is described by Ito et al., J. Biol. Chem. (1984) 48: 163-168; Brzobohaty and Kovac, J. of General Microbiology (1986) 132:3089-3093.